The aim of the invention is to reliably limit the period of use of such a device and meet safety requirements. The reasons for the limitation may be based on hygiene, medical or technical considerations.
The locking-stressing-mechanism, which is to be blocked after the permitted period of use has elapsed preferably comprises a helical thrust gear accommodated in a manually operated device, by means of which a rotary movement is converted into a linear movement and an operating spring is put under tension. The operating spring acts on a spring component of the locking-stressing-mechanism the movement of which is initially blocked as soon as the operating spring has reached the tensioned state. Secured in the spring component there may be a piston movably mounted in a cylinder. Inside the cylinder, in front of the piston, is a liquid which is expelled out through a nozzle as the locking mechanism of the locking-stressing mechanism is actuated by the piston driven by the operating spring. The number of actuations of the locking-stressing-mechanism and hence of the device can be counted by a mechanical counter.
WO-93/21980 describes a metered-dose inhaler. The dose of a substance to be inhaled is introduced, by means of a hand-operated device, from a supply of the substance contained in the inhaler, into a chamber from which the dose is expelled with the current of air which the user sucks in through the inhaler as they breathe in. The metered-dose inhaler is fitted with a counter which comprises a rotatable screw spindle and a rod, one end of which engages in the form of a nose in the thread of the screw spindle. The rod moves parallel to the screw spindle as the rotation of the spindle increases. The counter indicates, by means of the position of the nose-like end of the rod, the number of doses which have already been taken out of the supply of substance, or those which can still be taken out. The other end of the rod is movably held in a guide shaft into which the rod extends more deeply as the rotation of the screw spindle increases. As soon as the supply of substance in the inhaler is coming to an end, the nose-like end of the rod engaging in the screw spindle reaches that part of the spindle which has a number of courses of thread having a greater pitch than the rest of the screw spindle. As a result, on each rotation of the screw spindle, the rod moves along faster than before. The other end of the rod meanwhile bears on a flexible lever, and further actuation of the metered-dose inhaler is prevented.
WO-97/20590 describes a locking stressing mechanism for a spring-actuated output drive. WO-97/24586 describes a mechanical counter for a metering device. WO-97/12687 describes a device for generating high pressure in a fluid in a miniature arrangement provided with a locking stressing mechanism and a counter. The apparatus is used to atomise a fluid to produce an inhalable aerosol. WO-01/64268 describes a needleless injector which contains a locking stressing mechanism.
The pieces of equipment mentioned above by way of example are intended for repeated use, e.g. for repeated atomisation of a given amount of liquid to produce an aerosol for inhalation into the lungs, or for needleless injection of a given quantity of liquid underneath the skin of humans or animals. The quantity of liquid atomised or injected may contain a therapeutically active substance.
An object of the present invention is to provide a device for an apparatus which will reliably, effectively and finally prevent further use of the apparatus after a given number of actuations if there is a compelling reason for this. The apparatus comprises a locking-stressing-mechanism with an operating spring and a spring transfer member in which is accommodated a piston which is mounted to be movable in a cylinder. The components are housed in a two-part housing which comprises an upper housing part and a lower housing part. The two housing parts are mounted to be rotatable relative to each other. The operating spring is tensioned by means of a screw thrust gear by manually rotating the two housing parts relative to each other. At the same time as the housing parts are rotated relative to each other, a mechanical counter is actuated which comprises a threaded spindle and a slider. The threaded spindle is mounted in the wall of the lower housing part. The slider is moved up or down the spindle by an amount which depends on the number of rotations of the two housing parts relative to each other.
This problem is solved according to the invention by a device having the following characterising features:                A recess is provided in the outer wall of the lower housing part and in the inner wall of the upper housing part. The two recesses are opposite each other when the two housing parts are in a given rotary position.        In the recess in the lower housing part there is a movable blocking element which is located only in this recess before the blocking device is activated and allows the two housing parts to rotate relative to each other. After the activation of the blocking device the blocking element is located in both recesses and prevents the two housing parts from rotating relative to each other.        By means of a push-rod which co-operates with the slider on the spindle of the counter, the blocking element is moved out of its resting position into the position which it occupies after activation of the blocking device.        
On the one hand, the push-rod may be mounted on the slider to the side of the spindle of the counter. In this embodiment of the blocking device, during normal use of the device, the slider moves towards the upper spindle mounting and towards the upper housing part. The recess in the wall of the lower housing part is mounted next to the axis of the counter spindle. Before the slider makes contact with the upper spindle mounting, the push-rod moves the blocking element located in the recess in the wall of the lower housing part out of its resting position and thereby activates the blocking device.
The push-rod can also be constructed as an extension of the blocking element. In this embodiment, the end of the push-rod projects into the path travelled by the slider during normal use of the device before the slider comes to abut on the upper mounting of the counter spindle. This embodiment works in exactly the same way as the embodiment described above.
In another embodiment of the blocking device the push rod may be constructed as an extension of the counter spindle and may project beyond the upper spindle mounting. In this case the counter spindle is mounted to be axially moveable. The recess in the wall of the lower housing part is preferably provided on the axis of the counter spindle. Before the blocking device is activated the counter spindle is pressed against the lower spindle mounting by a spring, e.g. a helical spring. In this embodiment of the blocking device the slider moves towards the lower spindle mounting during normal use of the device. As soon as the slider comes to abut on the lower spindle mounting, the counter spindle moves axially towards the upper housing part as it continues to rotate. The extension of the counter spindle in the form of a push rod moves the blocking element located in the recess in the wall of the lower housing part out of its resting position, thereby activating the blocking device.
In a reversal of the embodiments described, the blocking element may be pulled out of its resting position by the slider.
The blocking element located in the wall of the lower housing part may be axially or radially moveable. The blocking element may be a leaf spring, preferably a pre-stressed leaf spring with two legs preferably made of metal.
The blocking device according to the invention has the following advantages:                It is suitable for miniaturised equipment.        It is arranged between the housing parts which overlap one another and in its position of use in a device it is inaccessible to the user.        It is easy to assemble.        A blocking element in the form of a pre-stressed leaf spring with two legs is secured against movement in its resting position without any additional effort.        A pre-stressed leaf spring can be pushed into or pulled out of its resting position with relatively little force.        A pre-stressed leaf spring with two legs jumps abruptly from its resting position into the position it occupies when the blocking device is activated, as soon as it has been moved a certain distance by means of a push rod. Thus the response point of the blocking device is precisely fixed.        The rotation of the two housing parts relative to one another is blocked directly as soon as the blocking element, which was originally located in the recess in the wall of the lower housing part, is situated in both recesses at the same time.        The activated blocking device which contains a pre-stressed metal leaf spring can only be overcome by a force moment amounting to several Newton metres, which will destroy the blocked device.        
The blocking device according to the invention is used for example in a high pressure atomiser or in a needleless injector. A medical liquid administered using such a device may contain a drug dissolved in a solvent. Suitable solvents include, for example, water, ethanol or mixture thereof. The drugs in question may be, for example, Berotec (fenoterol hydrobromide; 1-(3,5-dihydroxy-phenyl)-2-[[1-(4-hydroxy-benzyl)-ethyl]-amino]-ethanol-hydrobromide), Atrovent (ipratropium bromide), Berodual (combination of fenoterol hydrobromide and ipratropium bromide), salbutamol (or albuterol), Combivent, Oxivent (oxitropium bromide), Ba 679 (tiotropium bromide), BEA 2108 (tropenol di-(2-thienyl glycolate), flunisolide, budesonide and others.